1. Field of the Invention
This invention relates to chemical analyzers which automatically analyze fluids, and more particularly relates to “dry chemistry” analyzers. Even more specifically, this invention relates to chemical analyzers that are particularly adapted for biological fluid testing purposes wherein a change in an optical characteristic of a sample is sensed and analyzed automatically by the analyzer. The analyzer of the present invention has particular utility for human and veterinary applications.
2. Description of the Prior Art
Various analyzers have been developed for automated test procedures involving essentially dry, analytical elements, which elements offer substantial storage and handling conveniences. The “dry” analytical elements are preferably in the form of test slides. The test slides are formed as a multi-layer element containing the necessary free agents for reaction with components of a biological fluid, such as blood serum, deposited thereon. Certain reactions colorimetrically produce a change in optical density, which is sensed by a reflectometer or other device, the amount of light reflected from the test element varying in accordance with the reaction and being indicative of the amount of a particular component present in the fluid. Such test slides containing a dry analyte are well known in the art and are described in U.S. Pat. No. 4,647,431, which issued to Takasi Sekine, et al. Instruments utilizing dry slides are also known, such as the VETTEST® analyzer available from IDEXX Laboratories, Inc., Westbrook, Me. and the VITROS® analyzer available from Ortho-Clinical Diagnostics, Inc, Rochester, N.Y.
A very capable “dry chemistry” analyzer is described in U.S. Pat. No. 5,089,229, which issued to Thomas Heidt et al., the disclosure of which is incorporated herein by reference. The chemical analyzer described in the aforementioned '229 Heidt et al. patent includes a rotatable turntable which is adapted to hold a plurality of reagent test slides, a sample metering device, an incubator or temperature controller, a reflectometer, a slide injector mechanism, a slide ejector mechanism and associated electronics, computer or microprocessor, and software. The rotatable turntable preferably holds up to 12 slides about its circumference. The test slides come individually sealed. They are unsealed and immediately placed in the injector mechanism, which transfers the slides to the rotatable turntable. The turntable positions the reagent test slides under the metering device, which device deposits a predetermined amount of sample onto each slide. The turntable also carries the slides above a reflectometer. After testing has been completed, the ejector mechanism automatically removes the reagent slides from the turntable.
In the chemical analyzer described in the '229 Heidt et al. patent, the rotatable turntable is formed as an integral part of the chemical analyzer. It is not intended to be removed except in the situation where the chemical analyzer needs to be disassembled for repair. The dry analytical test slides come individually prepackaged, and are inserted by the operator onto the rotatable turntable one at a time by using the inserter mechanism. In routine testing of biological fluids, very often the same test slides will be used. There are times when multiple test slides containing the same chemical reagent are used concurrently in the test run, for redundancy, averaging of test results or for verification of test accuracy. Sometimes, for certain fluid tests, the operator may wish to select special reagent test slides not used in routine testing.